1. Field of the Invention
The present invention relates to a method for cleaning water, especially surface or waste water from buildings or roads, which water is directed to a sludge separator for separating suspended material. The invention also relates to means for carrying out the method.
2. Description of Related Art
Cleaning of sewage water from separate building or roads or small groups of houses has up til now been effected by a low degree cleaning wilt sludge separators, such as three compartment septic tanks. The water flows by gravity to the well in which coarse pollution sediment at the bottom of the wells. One to two times a year the well is emptied.
One type of sludge separator or septic tank is known from U.S. Pat. No. 4,997,562. The tank shown in this document is divided into a plurality of chambers in which the water to be cleaned is brought from each chamber to the next by means of a overflow valve so arranged that the chamber is filled with water up to a certain level before the water flow over to the next chamber. This is for preventing sedimented sludge to leave with the water. At the end of the separator a filter chamber is provided in which the water is filtered through sand and a fibrous organic material.
AT-B-396921 describes cleaning means in the form of a three compartment septic tank in which the water passes-one chamber for sedimenting sludge, one cleaning chamber and one filter bed. To increase the effect of the cleaning chamber, a plurality of walls are arranged so that the water is urged to flow in a loop through the chamber.
AT-363871 describes cleaning means with three or four chambers, namely, a sludge separator, a filter chamber, an aerating chamber and a final sedimenting chamber. In the filter chamber the water passes from the bottom of the chamber up through a biofilter.
Even if the use of sludge separators is an inexpensive and simple measure, the described cleaning measures, in accordance with higher environmental consiousness, are insufficient since they do not fully take care of biological material and/or phosphorus and not at all take care of heavy metals, which therefore come with the water to the recipient.
The main object of the invention is therefore to provide a method and cleaning means, which is simple and inexpensive to install and run, but notwithstanding this, result in a high degree cleaning of the water.
This object is achieved by giving the invention the features stated in the following claims.